In ff36ab34583a "dm: remove request-based logic from make_request_fn wrapper", device creation became a 2 stage process. In the first stage, the block device is created which has a queue set up but no mapping function set. This is done in the second stage, when the mapping table is supplied. At that stage the device can become either multi-queue/request based or doing the mapping on the bio level. So right now, it is possible to crash the kernel by doing a - dmsetup create --notable <name> - mount /dev/dm-<minor> <somewhere> While this may also need to be some fixing up in the device- mapper codebase, it also should be handled from the block core as allocating a queue can potentially be done separate from assigning a mapping function. There is already one check for not having set up a queue for a device, so this just adds an additional check for make_request_fn being unset before trying to further submit the requests. -Stefan Stefan Bader (1): blk/core: Gracefully handle unset make_request_fn block/blk-core.c | 7 +++++++ 1 file changed, 7 insertions(+) -- 2.17.1
